Elastic fluid turbine blading



1944- D. J. BLOOMBERG 2,355,413

] ELASTIC FLUID TURBINE BLADING Filed Jan. 21, 1942 P: A; r /6 Inventor:

i-jig Atto rn ey.

m. M David J. Bloombehg Patented Aug. 8, 1944 i i i David J. Bloomberg,Newton, Mala, assignor to I .General Electric Company, a corporation oiNew York Application January a1. 1942, Serial No. 427,601 6 Claims. (c1.ass-r7) The present invention relates to elastic fluid, turbine blading,more specifically to blading oi rotary bucket wheels. In elastic fluidturbines designed for constant speed and pressure condi- -tions ithasbeen the practice heretofore to provide bucket blades substantiallycrescent-shaped in cross-section and with constant entrance angle alongtheir entire length except in the case of bucket blades used for lowpressure turbine stages where in certain instances it has been customaryto take into consideration the diflerence between the rotationalspeed ofthe'outer'and in-. nor portions of such buckets and varythe entranceangle accordingly. It has been found that aside from differencesindiflerential speed present arrangements of turbine blading do not takeinto consideration changes in elastic fluid velocities due to frictionat-the inner and outer walls of nozzles for directing elastic fluidtowards the bucket blades. The buckets ordinarily aredee signed toattain best emciency with regard to the elastic fluid velocity obtainingin the central ormajor portion or the nozzles.

The objector my invention is to provide an for best efliciencywith'regard to the elastic fluid velocity existing near such portion.

For a consideration oi what I believe to be novel and my invention,attention is directed to the ijollowing description and the claimsappended thereto in connection with the accompanying the.

phragm it in the present example overlap with the bucket I! of thebucket wheel l0.

Adjacent partitions II form nozzles or passages for properly directingelastic fluid from one bucket wheel to a succeeding bucket wheel. Thevelocity of elastic fluid passing through a nozzle formed betweenpartitions II is approximately constant over an intermediate portion oi.the norzle area between the inner and outer diameters extending over alength of about 80% or the entire length of the partition ii. Thevelocity near the inner and outerportions of the nozzle decreases due tofriction along the end walls oi the nozzle and other sources of lossesand becomes in zero at the end wall. In Fig. l the dot-and-dash line 20is atypical velocity curve plotted over the radial length of anozzlebetween the inner and outer diameters. The velocity in for theintermediate portion oi the nozzle, as stated above,

20 issubstantially constant. The velocity or for the end portions of thenozzle decreases from m to zero at the nozzle wall.

In the velocity diagram oi Fig. 2 the vector to designates the wheelspeed. The vectors v1 and improved construction or elastic fluid turbine25 v: designate average velocities oi the elastic fluid bladingwherebyeach bucket portion is designed in the intermediate portions and the endportions respectively 0! the nozzle. The resultant of the vectors to andor is an and its angle towards the horizontal, that is the angle atwhich elastic fluid m is discharged iromthe nozzle and enters the bucketpassages, is designated with an. The resultant oi the vectors to and oris designated with as. Its angle towards the horizontal is as. In

. order to obtain best eiflciency for an elastic fluiw In the drawing m586mm as velocity an at an angle a: the bucket blade shoui.

7 view; partly broken away. oi. an elastic fluid turbine embodying myinvention: Fig. 2 is an explanetary view; Figs. 3,5 and 7 areperspective views of three modifications according to my invention: andFigs. 4, 6 and 8 are top views of the bladesin Figs. 3, 5 and 7respectively.

The arrangementin Fig. 1 comprises a bucketv wheel it! having a ring ordisk H with a plurality of circumierentlally spaced buckets I! attachedthereto. The blades of the buckets I! will be described hereafter.During operation elastic fluid is directed towards the bucket I! byanozzle dig aphragm I3 and the elastic fluid discharged from the bucketwheel is passed to anotherbucket wheel through the intermediary oianother nozale diaphragm it having a plurality of circumi'erentiallyspaced partitions I! held between an inner disk It and an outer ring I1.The diaphragms It and are supported on an outer casing or shell I. Thepartitions of the dia- II have an entrance angle equal to all. Such abucket blade is indicated in Fig. 2 in cross-section by referencenumeral II. with such cross-section best efliciency is obtained withregard to the indil termedlate portion only of the nozzle. In order toattain similar good emciency for the reduced esteem velocities near theend portions of the bucket blade I provide these end portions withentrance angles as. In Fig. 2 I have shown with in regard to the vector2:; a cross-section 22 oi a 60 ing from the crossseetion tito thecross-section II. The cross-section 2| has a sharp inlet edge with anentrance angle a1 while the cross-section 22 has a rounded inlet edgewith an entrance an gle as. The provision of end portions with largerentrance angles is particularly efl'ectlve in case of bucketsoverlapping the partitions from which they receive elasticfluid asindicated in Fig. 1 withregardto the buckets l2 and the partitions ofthe diaphragm l3.

The bucket in Figs. 3 and 4 comprises a base 23 with a blade 24 securedthereto. The blade 24 has an intermediate portion 25 which iscrescentshapedand has a cross-section corresponding to the cross-section2| Fig. 2. The blade 24 has a portionv 28 at each end which has across-section merging from a section corresponding to that 01 2| in Fig.2 towards a section or end race 21 corresponding to the section 22 inFig. 2.

- an entrance angle larger than that 01' the inter- As indicated in Fig.4 the entrance edge 28 oi! the bucket. is uniformly spaced along itsentire length from the center lineof the bucket. thev spacing beingindicated by the reference character 29. The blade arrangement as shownin Fig. 3 is very efficient but requires more machining due to theincreasing thickness of the entrance portion near the ends of the bladerelative to theintermediate portion.-

The arrangement in Figs. 5 and 6 requires littie additional machining ascompared with that of an ordinary blade with uniform entrance anglealong its entire. length. The bucket of Fig. ,5 has. a blade 30 securedto a base 3|. The crosssectionof the blade is essentiallycrescent-shaped along its entire length, as shown in Fig. 6. Endportions of the entrance edge I2 of the blade are.-;cut away, thusproviding a portion with an entrance angle gradually increasing from themediate portion.

2. A turbine blade of the kinddescribed, which blade has anintermediateportion with a sharp entrance edge Iorminga uniform entranceangle for elastic fluid and a portion at each end with an entrance edgeincreasing in thickness towards the end and-forming an entrance angleincreasing from vthatof the intermediate portion towards the end. i

3. A turbine bladeoi the kind described which has an intermediateportion essentially crescentshaped, in cross-sectionand havinga sharpinlet edge with .uniformsentrance angle, and an entrance portion ateachaend which has a crosssection equal to a part of the cross-sectionof the I intermediateportionwithpartsnotboth end porangle-p1 (Fig. 6)for the intermediate portion to the angle ,8: for the outer ends of theend portions. The spacing of the inlet edge, of this bucket from thecenter line is not uniform, however. At the outer ends the blade isspaced from the center line by a distance 33 which is less than thespacing 34 for the intermediate portion.

a bucket with a blade 35 fastened at its inner end to a base 36. Theblade has an intermediate portion 31 extending over at least 80% of theentire length of the blade and being essentially crescent-shaped incross-section. The blade has end portions 38, each having a length ofless than 10% of the entire length of the blade. These end portions aregradually bent backward in the direction of rotation on the inlet sidewith regard to the intermediate portion, as shown in Fig. 2. Theentrance edges of the end portions are-cut away so that the entranceedge of the entire blade is uniformly spaced from its center line.

tions near-the inlet edge-being gradually cut away in order to formentrance angles gradually increasing from that of the-intermediateportion towards the outer ends of the endportions.

4. A turbine blade of the kind-described which has an intermediateportion substantially crescent-shaped in cross-section and forming aconstant entrance angle and'a portion at each end also substantiallycrescent-shaped in cross-section and, having an entrance angle whichincreases from the inner end of such end portion towards its outer end.

5. In a turbine, a diaphragm having a plurality of circumferentiallyspaced partitions and a bucket wheel having a plurality; ofcircumIerentially spaced buckets with end portions overlappingcorresponding. end portions of the partitions, both end portions of eachbucket near its entrance edge beingcut away and forming entranceanglesfor elastic fluid largerthan the entrance angle of theintermediate bucket portions.

6. A turbine blade of the kind described, which blade has anintermediate portion with a sharp entrance edge and a portion at eachend bent back in the direction of rotation with regard to theintermediate portion .to form entrance angles increasing towards theouter ends of the end portions.

DAVID J. BLOOMBERG.

